Manufacturers and designers of integrated circuits continue to relentlessly decrease the size of integrated-circuit features, such as transistors and signal lines, and correspondingly increase the density at which features can be fabricated within integrated circuits. For example, the next generation integrated circuits and data-transmission architectures may include both electronics and optoelectronics to create high-density, high-speed, and high-capacity devices. Manufacturers and designers have begun to approach fundamental physical limits that prevent further decreasing feature sizes in such integrated circuits fabricated by conventional photolithography techniques. Recent research efforts have turned to new, non-photolithography-based techniques for fabricating nanoscale electronics and nanoscale optoelectronics that represent a significant decrease in feature sizes from currently available, submicroscale electronics fabricated by currently available high-resolution photolithographic techniques.
In one approach to designing and fabricating nanoscale functional devices, “one-dimensional” nanostructures, such as nanowires, and “zero-dimensional” nanostructures, such as quantum dots, can be fabricated by epitaxial growth on a surface of a single-crystal semiconductor substrate. In nanowire-based devices, nanowire junctions representing the closest point of contacts between adjacent nanowires may be fabricated to have properties of configurable resistors, switches, diodes, transistors, and other familiar electronic components of integrated circuits. In other approaches, nanowires with a crossbar architecture can be formed. The grid-like nanowire crossbars provide a two-dimensional array of nanowire junctions that can be configured to form a variety of different types of functional devices or sub-systems in electronics and optoelectronics. In addition to being used to form nanowire junctions, nanowires have also found utility in sensors, as interconnects, and in a number of other applications. Quantum-dot-based devices, which are a relatively more mature technology than nanowire-based devices, can be utilized in a various electronic and optoelectronic applications. Quantum dots formed by epitaxial growth can be used for forming various types of nanoscale-electronic and nanoscale-optoelectronic devices that take advantage of the unique properties provided by the nanoscale dimensions of the quantum dots.
Fabrication of nanowires and quantum dots has often been performed by epitaxially growing single-crystal nanowires or quantum dots on a surface of a suitable single-crystal semiconductor substrate to ensure high-quality epitaxial growth and to enable electrical access to individual nanostructures or groups of nanostructures. However, the cost single-crystal semiconductor substrates, such as single-crystal silicon wafers and single-crystal gallium arsenide wafers, are very expensive. Moreover, the world-wide demand for single-crystal silicon wafers appears to be rapidly increasing, which will further increase the price for single-crystal silicon wafers. Therefore, researchers and developers of nanoscale devices continue to seek more affordable and versatile material platforms and techniques to fabricate electrically accessible high-quality, single-crystal nanostructures for nanoscale functional devices.